Buggy code:
public class MainActivity extends ActivityBase implements ProximityListener , VisitListener { private final Context context = this ; private TextView lblLoggedInAs ; private Button btnMyAppointments ; private Button btnAvailableAppointments ; private Button btnPaypalpayment ; private static final String PROXIMITY_APP_ID = "0e7b20b165e3a495d199249915365f28d81a0a0a669f55834759001ebc5a8e91" ; private static final String PROXIMITY_APP_SECRET = "e16659d95bf6dcba77970c0d56a29c0822889d718d4eee630677ef8152939ca4" ; private StringBuffer sb = new StringBuffer ( ) ; private VisitManager visitManager = null ; private static final String TAG = "paymentExample" ; private static final String CONFIG_ENVIRONMENT = PayPalConfiguration . ENVIRONMENT_SANDBOX ; public String patientName = null ; double billedAmount = 0 ; private static final int REQUEST_CODE_PAYMENT = 1 ; private static final int REQUEST_CODE_FUTURE_PAYMENT = 2 ; private static final int REQUEST_CODE_PROFILE_SHARING = 3 ; private static final String CONFIG_CLIENT_ID = "AfSxvU77TJyalxLi9n28h-EQRY9YpBX5DqzJlkLnItQBKJtfkExnHtPvkEHa728-Trw-ffpnuCKjokmq" ; private static PayPalConfiguration config = new PayPalConfiguration ( ) . environment ( MainActivity . CONFIG_ENVIRONMENT ) . clientId ( MainActivity . CONFIG_CLIENT_ID ) . merchantName ( "Pay<seq2seq4repair_space>my<seq2seq4repair_space>medical<seq2seq4repair_space>charges<seq2seq4repair_space>through<seq2seq4repair_space>Paypal" ) . merchantPrivacyPolicyUri ( Uri . parse ( "https:////www.example.com//privacy" ) ) . merchantUserAgreementUri ( Uri . parse ( "https:////www.example.com//legal" ) ) ; @ SuppressLint ( "NewApi" ) @ Override public void onCreate ( Bundle savedInstanceState ) { } protected void setUiComponents ( ) { } protected void setUiEventHandlers ( ) { } @ Override public boolean onCreateOptionsMenu ( Menu menu ) { } public boolean onOptionsItemSelected ( MenuItem item ) { switch ( item . getItemId ( ) ) { case id . item1 : setContentView ( preferences ) ; <START_BUG> Intent intent = new Intent ( this , Preferences . class ) ; <END_BUG> startActivity ( intent ) ; return true ; case id . item2 : setContentView ( activity_heartrate_monitor ) ; Intent inent = new Intent ( this , HeartRateMonitorActivity . class ) ; startActivity ( inent ) ; return true ; default : return super . onOptionsItemSelected ( item ) ; } } private void initializeProximity ( ) { } private void startProximityService ( ) { } @ Override public void didArrive ( Visit visit ) { } @ Override public void didDepart ( Visit visit ) { } @ Override public void receivedSighting ( Visit visit , Date date , Integer rssi ) { } @ Override public void serviceStarted ( ) { } @ Override public void startServiceFailed ( int arg0 , String arg1 ) { } private void logMessage ( String msg ) { } @ Override public void onBackPressed ( ) { } public void onBuyPressed ( View pressed ) { } private PayPalPayment getThingToBuy ( String paymentIntent ) { } private void addAppProvidedShippingAddress ( PayPalPayment paypalPayment ) { } private void enableShippingAddressRetrieval ( PayPalPayment paypalPayment , boolean enable ) { } private PayPalOAuthScopes getOauthScopes ( ) { } @ Override protected void onActivityResult ( int requestCode , int resultCode , Intent data ) { } private void sendAuthorizationToServer ( PayPalAuthorization authorization ) { } public void onFuturePaymentPurchasePressed ( View pressed ) { } }

Fix:
Intent intent = new Intent ( this , PreferencesActivity . class ) ;